1. Preheat the oven to 200C/400F/Gas 6.2. For the burger, place the steak, Camembert and oregano into a bowl, season with salt and freshly ground black pepper and mix well.3. Place a 5cm/2in chefs' ring onto a small plate and press the burger mixture into the ring. Cover the ring with cling film and place into the fridge to chill for five minutes.4. Remove the burger from the fridge and remove the chefs' ring. 5. Heat the oil in a frying pan over a medium heat and fry the burger for 4-5 minutes on each side, or until golden-brown and cooked to your liking. Set aside to keep warm. 6. For the rösti, place the grated potato onto a clean tea towel and squeeze out the excess water into a bowl. Place the grated potato into a clean bowl, season with salt and freshly ground black pepper and a pinch of cayenne pepper and mix well.7. Heat the butter and oil and place two 5cm/2in chefs' rings into the pan. Carefully press the grated potato into the rings and fry for 3-4 minutes. Remove the rings, carefully turn the rösti over using a fish slice and cook for 3-4 minutes on the other side. Transfer to the oven and bake for ten minutes, or until crisp and golden-brown. Place the rösti onto a plate and set aside to keep warm.8. For the relish, heat the butter and oil in a saucepan over a medium heat and cook the onion until softened but not coloured.9. Add the brown sugar, stir well to coat the onions and cook until caramelised. Add the red wine and vinegar, bring to the boil and simmer until thickened. Season with salt and freshly ground black pepper.10. To serve, sandwich the burger between the two rösti on a serving plate and serve with a spoonful of relish.